1. Field of the Invention
The present invention relates to a technique for improving the light-shielding property, the degree of freedom of design, and the operation accuracy of a lens barrel for use in an imaging apparatus such as a digital camera.
Furthermore, the present invention relates to a technique for increasing the movement stroke of a lens group in a retracted state, for a lens barrel for use in an imaging apparatus such as a digital camera, while keeping the lens barrel thin.
2. Description of the Related Art
For a lens barrel, a configuration in which a front group and a rear group of a lens group barrel are cam-engaged and held so as to restrict the rotation of the front group and the rear group using a guide member having a key for rectilinear restriction is known. Japanese Patent Laid-Open No. 2007-219304 discloses a shooting barrel in which the outer periphery portion, which is positioned outside a rectilinear key in the radial direction, of a cam ring that relatively rotates adjacent to the rectilinear key is cut out.
In addition, as the shooting performance and portability of imaging apparatuses are improved, thinning of a retractable lens barrel is desired. Conventionally, a three-stage retractable lens barrel in which a front group and a rear group of lens barrel are cam-engaged with and held by a third-stage cam member is known. Japanese Patent Laid-Open No. 2004-317943 discloses a digital camera that has been thinned by retracting a part of a shooting lens to a preferable position during retraction.
A conventional lens barrel has a poor light-shielding property for external light, and a low degree of freedom of design in the arrangement of the interlocking section for a cam ring. In the configuration disclosed in Japanese Patent Laid-Open No. 2007-219304, the outer peripheral portion of the cam ring is cut out. Hence, when external light that is penetrated into the lens barrel has passed through the outer periphery of the cam ring to reach the imaging element, there is a possibility that such light may affect a shot image. Additionally, the arrangement of the interlocking section, which moves in association with adjacent members, of the cam ring is limited, resulting in a reduction in the degree of freedom of design.
Also, in the conventional configuration, the relative distance between the front group and the rear group is limited by the amount of movement by the cam groove of the front group and the cam groove of the rear group, which are arranged on the third-stage cam member. Therefore, it is difficult to balance reducing the length of the lens barrel in the optical axis direction in a retracted state as much as possible and obtaining a large change in the relative distance during lens driving.
Accordingly, the present invention provides a lens barrel that improves light-shielding property for external light and the degree of freedom of design relating to the arrangement of the interlocking section for the cam ring.
Furthermore, according to the present invention, a change in the relative distance between the front group and the rear group is increased in a thin-type retractable lens barrel.